1. Field Of The Invention
This invention relates to vents used to vent high pressures below a packer in a well, adjacent a producing formation, and more particularly, to a pressure and bar actuated vent which may be opened even when there is low pressure in the tubing string.
2. Description Of The Prior Art
A relatively high pressure and bar actuated vent is disclosed in co-pending U.S. patent application Ser. No. 425,626, filed Sept. 28, 1982, assigned to the assignee of the present invention. This apparatus includes a body with a piston slidingly disposed therein having an air chamber sealed by a break plug. A firing bar is passed through the tubing string to fire the perforating guns below the vent, and the bar breaks the plug as it passes through the vent. This opens the chamber to pressure in the tubing string. This fluid pressure acts on a shoulder on the piston forcing the piston to move and align ports thereon with production ports in the body. An improved version, shown in GeoVann Drawing No. 20-2482, has a piston which simply uncovers ports in the body when in the open position. A disadvantage to these apparatus is that the tubing must have some fluid in it for actuation. In fact, it is not recommended that these vents be used with less than 500 psi total pressure inside the tubing.
Another vent which is actuated by pressure applied in the tubing string is shown in U.S. Pat. Nos. 4,330,039 and 4,434,854 to Vann et al.
To solve the problem of low pressure tubing situations, a bar-actuated vent having a collet-type opening sleeve has been developed, as disclosed in U.S. Pat. No. 4,512,406 to Vann et al. For this apparatus, a special bar is dropped down the tubing which engages collet fingers and moves a valve sleeve to an open position uncovering ports in the body. After the sleeve has moved a predetermined distance, the collet fingers release the bar which then travels down the tubing string. A problem with this device is that the bars sometimes hang up inside the tool, which requires a separate operation to retrieve it and redrop it.
Other mechanically actuated vents are shown in U.S. Pat. Nos. 3,871,448 to Vann et al; 4,151,880 to Vann; and 4,299,287 to Vann et al.
The present apparatus solves the problems previously known by providing a low actuation pressure bar vent having a piston which can be opened by biasing means such as the force of a spring and the hydrostatic pressure in the well bore, or such as a pressurized gas chamber providing a force on the piston.